The present invention relates to an air bearing slider carrying a transducing head in a disc drive. More particularly, it relates to maintaining head media spacing (HMS) substantially constant between the transducing head and the disc.
Air bearing sliders have been extensively used in disc drives to appropriately position a transducing head above a rotating disc. In most high capacity storage applications, when the disc is at rest, the air bearing slider is in contact with the disc. During operation the disc rotates at high speeds, which generates a wind of air immediately adjacent to the flat surface of the disc. This wind acts upon a lower air bearing surface of the slider and generates a lift force directing the slider away from the disc and against a load beam causing the slider to fly at an ultra-low height above the disc. For the transducing head to read and write accurately, a specified HMS, or air bearing gap, must be maintained at the pole tip of the transducing head between the pole tip and the disc.
As disc storage systems are designed for greater and greater storage capacities, the density of concentric data tracks on a disc is increasing (that is, the size of data tracks and radial spacing between data tracks is decreasing). One aspect of achieving higher data storage densities in discs is operating the air bearing slider at ultra-low flying heights. The higher data storage (or recording) density requires the HMS between each transducing head and the rotating disc be reduced. As the HMS decreases, the amount of allowable HMS modulation decreases as well.
Typically the surface topography of the disc is rough and may have a waviness or a small frequency waviness called microwaviness. Microwaviness of the disc has a significant effect on HMS modulation. As the fly height between the slider and the disc becomes smaller and smaller, microwaviness causes a disturbance or vibration of the air bearing gap of the slider. Servo patterned media (SPM) is a disc where the servo patterns are not created magnetically, but rather by some other method. Typically stamping, or some other method, is used to create pits in the disc that represent the servo patterns. This rough and non-flat topography on the disc also causes the air bearing gap of the slider to modulate. When the air bearing gap modulates the transducing head cannot accurately read or write to and from the disc.
A slider flying over the disc responds globally to the changes in surface topography of the disc caused by microwaviness or SPM. Because the slider is a rigid body, the global response of the slider controls the local response of the transducing head, thereby resulting in HMS modulation. However, the global response of the slider to the topography is not well correlated to the local topography of the disc under the transducing head. Therefore, the HMS between the transducing head and the disc modulates resulting in inaccurate reading and writing of the disc.
There is a need in the art for a slider capable of maintaining the HMS substantially constant and minimizing the HMS modulation. Maintaining the HMS substantially constant between the transducing head and the disc permits the transducing head to read and write data accurately.